IE47511B1 - Compositions based on polypropylene and glass fibres - Google Patents

Abstract

A molding composition is comprised of (A) polypropylene, (B) glass fibers, (C) an unsaturated dicarboxylic acid imide, and (D) a thermoplastic elastomer, and is useful for the fabrication of a variety of shaped articles, especially for the automotive industry [e.g., radiators, battery casings, fans, etc.].

Description

The present invention relates to compositions based on polypropylene and on glass fibres.

It is known to improve the mechanical properties of thermoplastic polymers by incorporating glass fibres. However, such a combination can present problems of adhesion of the glass fibres to the polymer, and thus, where the polymer is polypropylene, it has been proposed (see French Patent 2,136,614) to mix a certain amount of bis-maleimide with the polypropylene and then prepare the composition which contains the glass fibres. The products prepared from this composition exhibit good mechanical strength but for various applications it appears that a high value of the flexural modulus is associated with poor impact strength at low temperatures.

The object of the present invention is to provide compositions based on polypropylene and on glass fibres which give articles which, in particular, exhibit a particularly valuable modulus of elasticity and a particularly valuable low temperature impact strength.' The compositions of the present invention comprise. A) a crystalline propylene hcmo- or co- polymer, referred to sinply as polypropylene, B) a ccmpound, possessing an imide group, of an ethylenically unsaturated dicarboxylic acid, C) glass fibres and D) ah amorphous thermoplastic elastcmeric ethylene pclymer.

The preferred amounts of the various constituents of these compositions are expressed as follows (by weight): the polypropylene A represents 30 to 99%, generally 50 to 99'ύ of the weight of the mixture of polypropylene A + thermoplastic elastomer D, the compound Bi possessing an imide group, represents 0.01 to 10% of the weight of the mixture of polypropylene A + elastomer D + glass fibres C, and the glass fibres represent 1 .to 50% of the weight of the mixture of polypropylene A + elastomer D + glass fibres C.

The polypropylene used in these compositions is generally selected from amongst the different varieties of crystalline polypropylene which contain at least 50% by weight of isotactic portions, and which have a melt index of 0.2 to 15, determined using Standard Specification ASTM 1238-72 (at 230° under a load of 2.10 kg), and a molecular weight of 250,000 to 700,000.

Such polymers can be prepared by application of known methods, such as the technique which employs a catalyst of the Ziegler-Natta type.

These polypropylenes can be propylene horaopolymers of propylene-ethylene copolymers which preferably contain up to 10% by weight of ethylene.

Amongst the copolymers, block copolymers containing polypropylene chains and elastomeric phases, which in turn consist of a propylene-ethylene copolymer in which the ethylene content can be up to 30% by weight, are preferred.

In the compositions according to the invention, the proportion of polypropylene in the abovementioned mixture of A + D is preferably from 50 to 95%.

In the compositions of this invention, the thermoplastic elastomer (D) is an elastomeric copolymer based on ethylene and generally on at least one other olefinic monomer, and has an essentially amorphous structure (degree of crystallinity less than 15%) and typically a Mooney ML-4 viscosity, according to Standard Specification NF T 43,005, of 20 to 120 at 121°C These copolymers can more specifically be ethylene/propylene copolymers which contain from 40 to 80% by weight of units derived from ethylene. It is also possible to use copolymers of ethylene and but-l-ene, or of ethylene and butadiene, or terpolymers, in particular terpolymers based on ethylene, propylene and an unsaturated acid such as maleic acid or an aliphatic diene, especially a non-conjugated diene such as penta-l,4-diene, 2-methyl-penta-1,4-diene, hexa-1,5diene, hexa-1,4-diene or 2-methyl-hexa-1,5-diene, or a diolefine with an endomethylene group, such as dicyclopentadiene, norbornadiene, methylene-norbornene or a cyclic diolefine such as cyclo-octa-1,5diene. As a general rule, the proportion of the third monomer, mentioned above, does not represent more than 5% of the weight of the terpolymer.

Such thermoplastic elastomers can be prepared by applying methods described in Encyclopedia of Polymer Science and Technology - 1967 edition, volume 6, pages 359 et seq.

The constituent B of the compositions according to the invention is a compound, possessing an imide group, and, more particularly, a mean value of at least 1.2, especially 1.2 to 5, imide groups of an unsaturated dicarboxylic acid. This expression denotes products, mixtures of products and macromolecular substances prepared under conditions such that the said compound contains n units of the formula CO N 47511 . 6 where n represents a mean value of 1.2 to 5 and G represents one of the following radicals: YC II YC and where Y represents H, CHj or Cl and z is 0, 1 or 2.

More particularly, the constituent B is a bis-imide or a polyimide containing from 3 to 5 imide groups, of an- unsaturated carboxylic acid, a mixture of a mono-imide and a said bis-imide and/or polyimide, and substances obtained from such bis-imides or polyimides and from compounds which contain groups capable of reacting with the groups represented by G to form macromolecular chains.

The constituent B can in particular be a bisimide of the formula CO CO CO N-R-N •CO where G has the meaning given above and R represents a divalent radical, which is: a linear or branched alkylene radical containing up to 13 carbon atomsι a cyclohexylene or cyclopentylene radical, a phenylene or naphthylene radical/ a radical of formula NH I \ - C N II If or ' N - C two phenylene radicals where s is 1, 2 or 3, or a radical comprising 10 joined to one another by a simple valency bond or by an atom or group such as -C^-/ -0-/ -CfCH^Jj-/ -S02or -S-.

Specific examples of such bis-imides include Ν/N1 -ethylene-bis-maleimide, N/N1 -meta-phenylene-bis15 maleimide, N/N'-para-phenylene-bis-maleimide/ N(N1-4/41-diphenylmethane-bis-maleimide, Ν/N'-4,4’diphenyl-ether-bis-maleimide, Ν,N'-4,4'-diphenylsulphone-bis-maleimide, N/N’-4,4’-diphenylmethanebis-tetrahydrophthalimide and N/N*-4/4'-diphenylmethane47511 bis-chloro-maleimide.

These bis-imides can be prepared by applying the methods described In U.S. Patent 3.018,290 or British Patent Specification No. 1,375,592.

Constituent B can also be a polyimide of the formula /“Χ G N CO' in which the symbol G has the meaning given above and the symbol represents a radical possessing m free valencies, m being preferably from 3 to 5 (as a mean value); in particular, this radical can consist of several benzene nuclei linked to one another by one of the abovementioned inert atoms or inert groups.

Such polyimides can be prepared by applying the method described in Belgian Patent 785,391.

Constituent B can also consist of a mixture comprising one or more of the abovementioned bis-imides or polyimides and one or more mono-imides of the formula CO N-R CO in which Rj represents a hydrogen atom or a monovalent) aliphatic, cycloaliphatic or aromatic hydrocarbon radical containing up to 20 carbon atoms.

Specific examples of such mono-imides include maleimide( N-phenylma le imide, N-phenyImethylmaleimide, N-phenylchloromaleimide, N-p-chlorophenylmaleimide, N-p-methoxyphenylmaleimide, 4-maleimido-41-acetoxysuccinimido-diphenylmethane) 4-maleimideo-4'-acetamidodiphenylmethane) N-vinylmaleimide and N-allylmaleimide.

These mono-imides, the proportion of which in the mixture with the bis-imides or polyimides should be such that the mean value of n is at least 1.2, can be prepared by applying the methods described, for example, in U.S. Patents 2,444,536 and 3,717,615 or in German Patent Application 2,354,654.

As indicated above, constituent B can also consist of a macromolecular substance containing, on average, n units of the formula CO CO (n having been defined above). Such substances can be prepared by reaction of a bis-imide or of a polyimide (and optionally of a mono-imide) with a compound containing groups which are reactive towards the unsaturated part of the said imides (represented by the symbol G), in such proportions, or under such conditions, that a part of the unsaturated acid imide groups remains unaffected by the reaction.

In practice, if m^ denotes the number of unsaturated imide groups introduced into the reaction by the compound possessing an imide group and m2 denotes the number of groups which are reactive towards this unsaturated group, introduced by the other reactant or reactants, the proportions used are such that the mean value of the ratio m^/m2 is from 1.2 to 10.

This other compound is one of the various products which are known to react with the imides of unsaturated carboxylic acids. Typical examples include the reaction products of a bis-imide or polyimide with a polyamine, especially with bis-primary diamines of the formula H2N-R'-NH2, in which the symbol R' is as defined under R above. The polyamines can also contain more than two -NH2 groups. Such polyamines can be represented by the formula (NH2^m,’R'l' which the symbols m' and R1^ are typically as defined above form m and respectively. These diamines or polyamines can be used either as a mixture of two or more different types of product, or as a mixture with primary monoamines or with secondary monoamines or polyamines. As regards the reaction of the compounds possessing an imide group with the compounds possessing an amine group, reference may be made to the following patents: French Patent No. 1,555,564 and Belgian Patents No. 785.392 and No. 774,376.

In the compositions of the present invention, such macromolecular substances are generally used at the prepolymer stage, that is to say at the stage where they contain some carbon-carbon double bonds of the compound possessing an imide group, capable of undergoing subsequent reaction. Such prepolymers are generally obtained by mixing and heating the reactants at 50 to 180°C for a length of time which makes it possible to obtain a polymer which is soluble in solvents such as dimethylformamide and N-methylpyrrolid-2-one and has a softening point in a temperature range fran 60 to 150°C.

The reaction product of the abovementioned bis-imides or polyimides with N-vinylpyrrolid-2-one can also be used as the macromolecular substance; the preparation of such products is described in Belgian Patent No. 846,365. In the present invention, such compositions or polymers are preferably used in the form of a powder. To do this, the polymers are partially hardened by heating to a temperature from, say, 80 to 180°C; the polymer obtained generally has a 4-7511 softening point from 30 to 150°C.

The polymers defined above, and resulting from the reaction of bis-imides or polyimides with a polyamine or with N-vinylpyrrolidone, can be used as obtained, or can be modified by adding various substances. In particular, there may be mentioned the addition of unsaturated polyesters or of solutions of unsaturated polyesters in a polymerisable monomer. As regards the polymers obtained from polyimides, reference may be made, concerning the addition of unsaturated polyesters, to Belgian Patent No. 771,831 and, as regards N-vinylpyrrolidone, to the abovementioned Belgian Patent No. 846,365. Examples of polyesters which can be used, include the polyesters obtained from aleic acid and from transnadic acid and from propylene glycol and ethylene glycol, such polyesters being used preferably in the form of a solution in allyl phthalate.

It is also possible to use, as a macromolecular substance, the product obtained from a bis-inn.de or a polyimide and a polyisocyanate such as those described in British Application No. 76/39874. The reaction between these two products consists essentially of an addition reaction of the NCO group with one of the unsaturated carbon atoms of the compound possessing an imide group. As indicated above, the amounts of reactants used in the invention are such that imide groups carrying double bonds remain in the compositions according to the invention. For the purposes of the present invention, the term polyisocyanate denotes a compound containing at least two NCO groups; it is to be noted that mixtures of polyisocyanates having different numbers of NCO groups can be used. According to the well known isocyanate chemistry, these products can consist of monomers (products of relatively low molecular weight) or of prepolymers.

The following products may be mentioned by way of specific examples of monomers: 2,4-diisocyanatotoluene, mixtures of 2,4-diisocyanato-toluene and 2,6-diisocyanato-toluene, bis-(4-isocyanato-phenyl)15 methane, 1,5-diisocyanato-naphthalene, para-phenylenediisocyanate, meta-phenylene-diisocyanate, tris(4-isocyanato-phenyl)-methane, 2,4-diisocyanatochlorobenzene, bis-(4-isocyanato-phenyl)-ether, 1,6-diisocyanato-hexane, 3,31-dimethyl-4,4'-diisocyanato20 diphenyl, bis-(4-isocyanato-cyclohexyl)-methane, bis-(3-methyl-4-isocyanato-phenyl)-methane, bis-(4-isocyanato-phenyl)-propane, 4,4'-diisocyanato3,31-dichlorodiphenyl and the polyisocyanates of the formula where w is from 0.1 to 4 (mean value).

The polyisocyanate prepolymer can be obtained by reacting a molar excess of diisocyanate with a 5 polymer containing at least two hydroxyl or amino groups. Such a polymer with hydroxyl groups can consist, for example, of polybutadiene containing hydroxyl groups, the long chain hydroxylated material present in castor oil, epoxy resin containing hydroxyl groups or, preferably, a polyester or polyether with terminal hydroxyl group.

The preparation of such prepolymers is described, for example, by SAUNDERS in Polyurethane Chemistry and Technology, Part I- 1962.

The compositions according to the invention also contain glass fibres (C). The amount of glass fibres preferably represents 10 to 40% of the weight of the mixture of A + B + C + D, These glass fibres preferably have a length of 100μ to 12 mm and the diameter of the unit filaments is generally from 2 to 20μ. Type E fibres (as defined in the Handbook of Reinforced Plastics - 1964 edition, page 120), the gauge of which (weight per kilometre of yarn) is from 600 to 2,500 dtex, are preferred. Though the E fibres are considered to be particularly suitable for the applications for which the compositions according to the invention are intended, it is possible to use other fibres either exclusively or in combination with E fibres. The abovementioned work (pages 121-122) gives examples of such fibres.

In general, glass fibres which have been treated are used in this invention. On the one hand, these fibres can be in the form of bundles of fibres by using a binder. Examples of such binders include polyvinyl acetate, copolymers of ethylene with esters of acrylic acid, epoxy resins and aromatic polyethers and polyesters. On the other hand, the fibres can be treated by means of a sizing agent, such as organosilicon compounds such as vinyl-tri-(ethoxymethoxy)-silane, γ-aminopropyltriethoxy-silane, 3-(2-aminoethylamino)propyl-trimethoxy-silane and vinyl-(methacryloyl)trimethoxy-silane and compounds such as the complexes of chromium with methacrylic acid.

The compositions according to the invention can be prepared by simply mixing the various constituents (A, B, C and D). According to a preferred technique, the process is carried out in two stages: in the first place the polypropylene, the thermoplastic elastomer and the compound possessing an imide group are mixed, and then, after having homogenised the mixture, the glass fibres are introduced whilst continuing the homogenisation operation. These operations are generally carried out at ambient temperature (from 15 to 30°C). The composition thus prepared can subsequently be directly compression-moulded at a temperature of say, 180 to 260°C or under a pressure of say, 100 to 400 bars, or be extruded at a temperature of say, 180 to 260°C and then granulated, and compression-moulded or injection-moulded at a temperature of say, 180 to 260°C and under a pressure of say, 200 to 1,500 bars. This second technique is usually employed because of the ease of operation which it offers.

The articles prepared from compositions according to the invention exhibit a number of valuable properties. They are particularly noteworthy in respect of the modulus of elasticity, the low temperature impact strength and the creep resistance. The methods of determination of these properties are indicated later.

Due to these properties, the compositions according to the invention are particularly suitable for the production of articles used in the automobile industry (radiators, accumulator boxes and fans) 47811 and for the manufacture of blanks for machining in place of light alloys.

The Examples which follow further illustrate the present invention. Xn these Examples, the products and the tests are as follows: Polypropylene (polymer A^ in the tahle): polypropylene containing 95% of isotactic portions, and having a melt index of 5 (under the conditions defined above) and a mean molecular weight of 320,000. 47SH Propylene copolymer (polymer A2): a block copolymer comprising polypropylene and elastomeric phases, the latter consisting of a copolymer of propylene and ethylene (70/30 by weight), the block copolymer containing, in total, 90% by weight of propylene and 10% by weight of ethylene. This copolymer has a melt index of 3.5 (under the conditions defined above) and a molecular weight of 360,000.

Bis-maleimide; Ν,N'-4,4'-diphenylmethane-bismaleimide.

Polyimide prepolymer (polymer B): a product obtained from 75 g of bis-maleimide, 12.5 g of N-vinylpyrrolidone and 12.5 g of a solution composed of 40% of diallyl phthalate and 60% of a polyester obtained from maleic acid, propylene glycol and ethylene glycol. This product, prepared by mixing the constituents at 120°C, is subsequently placed in an oven at l4o°C for 35 minutes to give a powder of softening point 71°C.

Glass fibres; glass fibres of type E CqJ fibres with a strand length of 6 mm, these fibres being bonded by means of an aromatic polyether and « treated by means of a size consisting of a Y-aminopropyltriethoxysilane.

Cg! fibres 6 mm long, bonded by means of an epoxide resin and treated by means of vinyl-tri(ethoxymethoxy)-silane (size).

C^: fibres 6 mm long, bonded by means of an aromatic polyether and treated by means of a chromium complex.

Thermoplastic elastomer (polymer D): an elastomer prepared from ethylene, propylene and a diene monomer, the elastomer having a high ethylene content (70%) and a low content of hexane-1,4-diene, and having a MOONEY viscosity [ML (1+4) at 121°C] of 60 + 6.

Tests: flexural modulus Standard Specification ASTM 0790-63, CHARFY impact strength Standard Specification ASTM 0256-56.

EXAMPLE 1: The following mixture is homogenised on rollers for 10 one minute: parts of a composition based on polypropylene and consisting of 50% by weight of polymer powder A2, defined above, and 50% by weight of thermoplastic elastomer D, 0.6 part of N,N’-4,4'-diphenylmethane-bis-maleimide and parts of glass fibres C^.

This mixture is extruded at 210°C on a single-screw extruder. The strand obtained on leaving the extruder Is granulated and injection-moulded at 24o°C in an injection-moulding machine, the mould of which is left at 25°C [pressure 1,350 bars, back-pressure 150 bars].

The mechanical properties measured on the shaped articles are shown in Table 1.

EXAMPLES 2 to 7: The various experiments carried out under the conditions described in Example 1, but using varying proportions of the different products, are summarised in Table 1.

The reference samples are prepared under the same conditions as those indicated in Example 1, but without addition of elastomer B.

The comparison between the experiments according to the invention and the reference samples shows that only the articles produced from compositions containing the thermoplastic elastomer exhibit both a high modulus and also a good low temperature (-20°C) impact strength.

EXAMPLE 8: Example 1 is repeated, replacing the N,N'-4,4'1° diphenylmethane-bis-maleimide by polymer B (obtained from the abovementioned bis-maleimide and N-vinylpyrrolid-2-one) The moulded articles obtained have a flexural modulus of 2,330 MPa at 23°C, and an impact strength of _ 10.56 kg.cm/cm^ at -20°C.

TABLE 1 Ex- amples Nature of the polypropylene Ratio of poly— pxpjSaie to elastomer D Nature of the glass fibre, and. content thereof* Content of bis-malelmid^in Modulus at 23°C ln MPa Impact drsigth at-arc,in Kg.a^fcur 1 polymer Ag 1 3OS4 of Cj 0.6 2,150 11.37 2 polymer Ag 1 30% of C2 0.3 2,416 9.7 3 polymer Ag 3 30# of Cj 0.3 3,133 7.45 4 polymer Ag 1.5 40# of Cj 3.0 3.930 11.26 5 polymer Ag 0.5 40% Of Cj 3.0 3,655 8.72 6 polymer Aj 7 30% Of Cj 1,0 4f650 8.10 7 polymer Aj 7 30% Of Cj 1.0 4,500 8.8 Refer- ence sample polymer Aj polymer Ag - 30% of Cj 30% of Cj 3.0 1.0 4,623 4,230 5.2 5.05 * as a percentage of the mixture of polypropylene + fibres + elastomer.

Claims (19)

1. A composition comprising a crystalline propylene homo- or co-polymer (A), an imide-groupcontaining compound of an ethylenically unsaturated 5 dicarboxylic acid (B), glass fibres (C), and an amorphous thermoplastic elastomeric ethylene polymer (D).

2. A composition according to claim 1, in which: the propylene polymer A represents 30 to 99% 10 by weight of the mixture of the propylene polymer A + elastomer D, the compound B represents 0.01 to 10% of the weight of the mixture of propylene polymer A + elastomer D + glass fibres C, and 15 the glass fibres C represent 1 to 50% of the weight of the mixture of the propylene polymer A + elastomer D + glass fibres C.

3. A composition according to claim 1 or 2, in which the propylene polymer is a crystalline 20 polypropylene containing at least 50% by weight of isotactic portions and having a molecular weight of 250,000 to 700,000.

4. A composition according to any one of claims 1 to 3, in which the thermoplastic elastomer is a copolymer based on ethylene and on at least one other olefinic monomer, has an essentially amorphous structure· and has a MOONEY ML-4 viscosity of 20 to 120 at 121°C.

5. 5. A composition according to claim 4» in which the elastomer is an ethylene/propylene copolymer containing from 40 to 80% by weight of units derived from ethylene.

6. A composition according to any one of 10 claims 1 to 4· in which the elastomer is a terpolymer based on ethylene, propylene and either an unsaturated acid or a non-conjugated aliphatic diene.

7. A composition according to any one of claims 1 to 6. in which compound B is a product. 15 mixture of products or macromolecular substance, which contains n units of the formula z co \ G N where n represents a mean value of 1.2 to 5 and G represents one of the radicals YC and YC - ( C h 3 ) z where Y represents H. CHj or Cl and z is Ο, 1 or 2.

8. A composition according to any one of claims 1 to 7, in which compound B is a bis-imide, a 5 polyimide containing 3 to 5 imide groups, a mixture of a bis-imide and/or a said polyimide with a monoimide, or a reaction product obtained fran the a bis-imide or a said polyimide together with a compound containing one or more groups capable of reacting with the 10 unsaturated group derived from the dicarboxylic acid to form one or more macromolecular chains.

9. A composition according to claim 8 in which compound B is a macromolecular substance obtained by reaction of the bis-imide and/or polyimide with a 15 polyamine, N-vinylpyrrolid-2-one or a polyisocyanate.

10. A composition according to any one of claims 1 to 9, in which the glass fibres (C) are of type E and 100μ to 12 mm long.

11. A composition according to claim 10, in 20 which the glass fibres are in the form of bundles, secured by a binder. 47S11

12. A composition according to claim 11, in which the binder is polyvinyl acetate, a copolymer of ethylene with an ester of acrylic acid, an epoxy resin or an aromatic polyether or polyester.

13. A composition according to any one of claims 1 to 12, in which the glass fibres have been treated with a sizing agent.

14. A composition according to claim 13, in which the sizing agent is an aminosilane, a vinylsilane or a chromium complex.

15. A composition according to claim 1 substantially as described in any one of Examples 1 to 8.

16. A process for preparing a composition as claimed in any one of the preceding claims which comprises mixing the specified ingredients.

17. A process according to claim 16 substantially as described in any one of Examples 1 to 8.

18. A composition as defined in claim 1 whenever prepared by a process as claimed in claim 16 or 17.

19. An article obtained by moulding a composition as claimed in any one of claims 1 to 15 and 18.